Tension mooring device

ABSTRACT

A tension mooring device for vessels is inclusive of a marinesituated platform on which a pneumatic-hydraulic cylinder mechanism is mounted. Included in the mechanism is a piston reciprocable to define a variable volume in the cylinder which is augmented by a closed air reservoir. There is at least one sheave mounted on the platform over which a cable is reeved. The cable is connected to move with a rod on the piston for transference of forces therebetween. A shackle at one end of the cable is provided for the connection of a mooring line from a vessel. The arrangement is such that variable air pressure in the cylinder and reservoir maintains a tension on the cable and correspondingly on the mooring line to accommodate motion of a moored vessel without damage.

a l 1 1 a 1! Elite tas atet 1 1 1 1 1 9 White et al. Feb. 11, 1975 [5 TENSION MOORHNG DEVICE 689.426 6/1964 Canada .1 114/230 58l,48l 81958 It'l [75] Inventors: Mlle" Miles Wh'le, Moraga; 1,174,901 11l1958 Fi aiice 114/230 Howard John Bates, Danville, both of calm Primary ExaminerTr ve M. Blix y [73] Asstgnee: The lRucker Company, Oakland, Assistant ExaminerEdward R. Kazenske Calif. Attorney, Agent, or Firm--Lothrop & West [22] Filed: Aug. 22, 1973 21 Appl. NO.Z 390,387 [571 ABSTRACT A tension mooring device for vessels is inclusive of a marine-situated platform on which a pneumatici i g gfi hydraulic cylinder mechanism is mounted. Included in 581 Field 61 Search 114/230, 215; 254/172, mechamsm a define 254/189 variable volume in the cylinder which 1s augmented by a closed air reservoir. There is at least one sheave mounted on the platform over which a cable is reeved. [56] References Cited The cable is connected to move with a rod on the pis- UNITED STATES PATENTS ton for transference of forces therebetween. A shackle 2,58l,676 l/l952 Loaney ll4/23O at one end of the cable is provided for the connection 3,()5l,448 8/l967 Pletta ll4/230 of a mooring line from/a Vessel. The arrangement is 3.057162 10/1962 Lee 224/13; Such that variable air pressure in the cylinder and 513 et 3 1x ervoir maintains a tension on the cable and correg 7/1973 i: 254/172 spondingly on the mooring line to accommodate motion of a moored vessel without damage.

FOREIGN PATENTS OR APPLICATIONS 626,493 2/1936 Germany 254/172 1 Clam, 2 Drawmg e TENSION MOORHNG DEVICE There is an increasing need for ways of mooring vessels to drilling platforms and the like often isolated in location and exposed to severe rigors of the open sea. The positioning of a vessel with respect to the platform is difficult since sea motion is apt to induce collisions and to snap mooring lines or cables.

It is therefore an object of our invention to provide a tension mooring device that can readily be utilized in connection with a drilling platform, for example, and that will afford a safe, effective mooring for the vessel.

Another object of the invention is to provide a tension mooring device which will maintain a predetermined or established tension on a mooring line despite movement of a vessel moored thereby and will maintain the tension with tractable limits.

Another object of the invention is to provide a tension mooring device that can readily be applied to existing drilling platforms without interfering with other mechanism supported thereon.

An additional object of the invention is to provide a mooring device that is effective to transfer mooring strains in a satisfactory fashion between a drilling platform and a moored vessel.

A further object of the invention is to provide a tension mooring device that is effective for multiple moormg.

A still further object of the invention is in general to provide an improved mooring device.

Other objects, together with the foregoing, are at tained in the embodiment of the invention described in the accompanying description and illustrated in the accompanying drawings, in which:

FIG. 1 is an isometric view, partly diagrammatic, showing a typical tension mooring device in position for operation; and

FIG. 2 is a side elevation, partly diagrammatic and with portions broken away, illustrating a portion of the cylinder and piston mechanism utilized in the tension mooring device.

While individual installations may vary substantially depending upon the surroundings, a typical successful mooring device installation is inclusive of a drilling platform 6 of an exemplary type having supports 7 suitably anchored or installed to maintain an upper platform 8 in a desired location and at a desired altitude.

In accordance with the invention, the platform 8 at a convenient location and preferably out of the way of other gear thereon is provided with a support frame 9 serving as a base for a vertically mounted cylinder 11. The cylinder is generally closed except for a packed opening 12 through which a piston rod 13 extends. The rod 13 is vertically reciprocable within the cylinder and at its lower end is joined to a piston 14. The cylinder interior is connected through a pipe 16 with an air-oil closed reservoir 17. A filling connector 18 and a release valve 19 are situated at the upper end of the reser- VOll'.

Also joined to the cylinder 11 preferably near the upper end thereof above the piston 14 is a connector 2l leading to the interior of a relatively small chamber 22 adapted to contain some air as well as some surge oil from the cylinder 11 above the piston 14.

The upper end of the piston rod 13 carries a freely rotatable pulley 26 in general alignment with a pair of pulleys 27 and 28 appropriately mounted within the base 9. A cable 29 is reeved on a sheave 30 having a vertical pivot connection 32 to the platform 6, for example, on a support 7 thereof. The end of the cable carries a connecting shackle 32 while the cable itself is reeved over a sheave 33 suitably mounted adjacent one corner of the platform 8. The cable then passes over one of the pulleys 27 or 28 and then is reeved around the pulley 26. From there the cable extends around the other of the pulleys 27 or 28 and then around a corner sheave 34. Finally the cable passes through a second sheave 36 comparable to the sheave 30 and terminates in a second shackle 37.

For operation, the hydraulic piston 14 is disposed at a low position within the vertical cylinder 11. The main air-oil reservoir 17 is filled partly with oil and at the top with air under a pressure substantially greater than atmospheric. Also, some oil is filled] into the chamber 22 and above the piston 14 and some air is likewise entrapped in this volume. Under these circumstances the pulley 26 is in a low position and the shackles 32 and 37 can lie relatively loosely with respect to their adja cent sheaves 31 and 36. For the mooring ofa single vessel the cable can be so positioned as to locate one ofthe shackles, such as 32, close to the sheave 30, whereas a stop is put on the other end portion of the cable adjacent the sheave 36 spaced somewhat away from the shackle 37.

A vessel to be moored is then brought into the vicinity of the platform and one end of the vessels bow mooring line is connected to the somewhat drawn out shackle 32. The vessel can be anchored or in any other fashion provided with a stern line which is close hauled. This puts some initial tension on the cable 29. Thereafter as the vessel heaves and tends to pay out the mooring line, the air pressure within the reservoir 17 is effec tive to displace oil therefrom into the cylinder 11 and to lift the piston 14 and the piston rod 13 so as to raise the pulley 26. This is effective to take in the shackle 32 toward the sheave 30 and to maintain tension in the stern line as well as in the mooring line. The vessel is well held in its located position.

When the vessel heaves to take in line, the shackle 32 is moved farther away and the cable 29 is correspondingly tensioned to lower the pulley 26. This correspondingly lowers the piston rod 13 and piston 14 to displace oil from the cylinder 11 into the reservoir 17 compressing the trapped air in the upper portion thereof. Consequently, the prescribed tension is still maintained on the mooring line as well as the stern line. Thus, despite heaving of the vessel, it is always maintained substantially in position between a pair of tensioned lines.

For the mooring of two vessels the same procedure is followed except that each vessel is attached to a respective one of the shackles 32 and 37. In this case the cable 29 in effect is reeved freely and can be displaced with regard to the two sheaves 30 and 36 but any difference in motion of the vessels allowing paying out or taking in of the cable is immediately responded to by a corresponding motion of the piston 14 shifting the pulley 26 so as to maintain the desired, predetermined cable tension.

As illustrated in FIG. 1, a comparable setup can be afforded along the other side of the platform 8 so that it is possible to accommodate four vessels at one time at a single drilling platform and maintain each of the vessels substantially in its preferred position at all times.

What is claimed is:

l. A tension mooring device for use in mooring vessels to a marine platform, comprising: an upstanding cylinder mounted on said platform, a piston vertically slidable in said cylinder and defining upper and lower variable volume chambers in said cylinder, an upstanding closed air-oil reservoir adjacent said cylinder, a conduit communicating the lower portion of said reservoir to the lower chamber in said cylinder, a body of oil in the lower portion of said reservoir and extending through said conduit into said lower chamber, a body of air confined in said reservoir above said body of oil,

piston downwardly in said cylinder. 

1. A tension mooring device for use in mooring vessels to a marine platform, comprising: an upstanding cylinder mounted on said platform, a piston vertically slidable in said cylinder and defining upper and lower variable volume chambers in said cylinder, an upstanding closed air-oil reservoir adjacent said cylinder, a conduit communicating the lower portion of said reservoir to the lower chamber in said cylinder, a body of oil in the lower portion of said reservoir and extending through said conduit into said lower chamber, a body of air confined in said reservoir above said body of oil, means adjacent said cylinder defining a closed pressure chamber of lesser volume than said reservoir, conduit means connecting the upper portion of said pressure chamber to the upper portion of said upper cylinder chamber, a piston rod secured to said piston and extending upwardly out of said cylinder, a sheave journalled on said piston rod outside said cylinder, and a cable reeved on said sheave and having means for securing the same to a vessel, said cable being directed from said sheave so that tension in said cable urges said piston downwardly in said cylinder. 